Power system



July 1, 1924. 1,499,542

C. MACMILLAN rowan sysmxmay.

g a E 1 n m =6 ampbell Macfn illan w v C m 1 5 43 M Hls Abto '60 of ship propulsion Patented July. 1, 1924.

umran srA'rss PATENT oar-lea.

OAIPBm normals, SGEENEG'IADY, NEW YORK, ASSIGNOB TO G nuc- TBIO comm, A CORPORATION OI NEW YORK.

POWER SYS'IEI.

To all whom it concern:

I Be'it known 01%,CAMPBEILMACMILLAN, a citizen of the United States, residing at Schenectady, county of Schenectady, State 5 of New .York, have invented certain new and useful Improvements in Power Systems, of which the following is a specification.

- My invention relates to power systems and more uparticularly to systems of electric ship prop s1on comprising propeller motors constructed and correlate in such manner as to effect a marked saving in the weightand cost of the electrical equipment.

In induction motor equipments for electric ship propulsion it is practically necessary to use higher voltages with increasing horse-power in order to avoid large cur- .rents which necessitate the provision of excessively large-cables and control switches.

High voltages, however, involve the use of more insulation which necessarily increases the size of the motor and, if the motor is to have two running speeds in ratios as great as two to one, its weight is further in creased due to the unfavorable utilization of active material which follows from the use of winding coils which are a compromise between those most suitable for different speeds, since in order to avoid great complication in switching it is ractically necessary to use 120 degree phase elts or in other words to segregate the coils into three grou 5 per pair of poles in the low. speed win mg connection, thereby lowerin the efliciency and power factor. I have ound that a saving of over, 15% in the wei ht" of the motor equipment is realized b usm in conjunction a motor insulated or the system voltage and wound for about one half the system voltage, and a motor insu lated and wound for aboutone half the system voltage and provided with a primary I winding arranged to produce different num- 46 here of poles.

An object ofmy invention is to provide a. motor equipment which may be economically constructed and efficiently operated.

' A further object is to provide a system havin an improved arran ement of the rope er motors.

y invention wil be better understood from the following description taken in connection with the accompanying drawings,

- 5 throu 11 Application fled Kay 11, 1923. Serial Io. 888,416.

and its scolpe will be pointed out by the ap nded c aims.

eferring now to the drawing, Fi 1 shows a system of ship propulsion in w 'ch my invention has been embodied, and Figs. 2, 3 and 4 show various schemes of connection which may be utilized in the operation of the system.

Fig. 1 shows a turbine 1 arranged to drive an alternating current enerator 2 provided with a polyphase win in 3 and a direct current field winding 4 which ma be supplied with current from any suita le source suitable excitation controlling means i1 ustrated; as an adju'stable rheostat 6. Provided for the purpose of regulating the supply of current from the nerator 2 to the propeller motors 7 and 8 1s a controller 9 of an suitable type arranged in the full spec ahead osition to interconnect the generator an motors as indicated in Fig. 4, inthe '1 low speed ahead position to interconnectithe generator 2 and the motor 8 as indicated in Fig. 2, and in the reverse position to interconnect the generator 2 and motor 8 as indicated in he induction motors 7 and 8 are wound for the same voltage between terminals but differ from each other in that the motor '2' is constructed for single speed operation and is insulated for a comparatively high voltage to ground while the motor 8 is arra d for operation at two different speeds an is insulated for a much lower voltage to ground. Assuming the generator voltage to be 5000, the motor 7 is wound for 2500 volts but insulated for 5000 volts while the motor 8 is wound for 2500 volts and insulated for about 3000 volts. In this arrangement the motor 7 may be wound with the most favorable coil pitch, owing to the fact that it is required to operate only at a single tipeed, but must have its stator coils insula for the full generator voltage which is a dis advantage both with respect to the additional insulation r uired and the increase in size necessitated by reason of the larger space occupied by the insulation. The motor, 8 is connected to the common neutral point and for this reason need have its stator coils insulated onl for about one-half the generator voltage ut is required to operate at difl'erent speeds and must therefore be one motor to operate under the disadvan-,

tages incident to high voltage insulation and arranging the other motor to operate under the 'sadvantages which follow from operation on difierent setsof ole numbers a very material saving in t e cost and weiht of the motor equipment may be the controller 9 to be in the 7 position diagrammatically shown in Fig. 1,

the shi ma be brought from rest to low s eed sad i moving the controller to the ow s ead position in which the nerator stator winding is connected in elta and the stator winding of the motor 8 is connected for the higher number of poles. To bring the ship up to full s eed ahead the controller is moved to the full g m ahead position in which the generator is connected in Y and is adapted to supply current to the motors 7 and 8 which are connected in series, the motor 8 being connected to the neutral point and arran ed for operation on the lower number of po es. In order to reverse the direction in which the ship is driven the controller must be moved to the reverse position in which the generator is connected in Y to the motor 8 or operation on the hi her pole number under which conditions t e highest reversing torque is available. When the ship is reversed the reversing motor 8 reuires so much current that the voltage of t e generator even when connected in Y is pulled down to a value suitable for use with the low voltage motor. As'the motor reve and comes up to s eed in the astern direction the generator vo tage will rise and may be maintained withinsuitable limits by manipulating the generator field rheostat 6 or in any other suitable manner.

In the case of induction motor equi ments of large capacity the subdivision of t e motor equipment into two units per shaft in .-stead of one is advantageous in that it en- I with m ables the rotor units to be kept within practicable dimensions and facilitates the provision of adequate ventilation. 'It is very dificult to secure a sufiicient supply of air we single unit when the ratio of Ion h to diameter becomes excessive. It shoul also be noted that the segregation of the functions between the two units in accordance invention generally permits the use of i entical stator punchin and, when dedrable, identical rotor punc g in both units. It is possible. to operate both motors at the same maximum current densities in stator co per. and also at approximately the phase due to the com romise in coil. pitch while the single spe motor has less current per slot due to thejfact that the slot currents are more nearly in' phase. It is therefore possible to reach a maximum permissible value of current er slot in each case without excessive slot imensions.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1. A powerv system comprising an alternatin current enerator, a .motor insulated for e full vo tage of said "generator and constructed for operation on a single pole number, a motor insulated for approximate- 1y one-half the voltage of said generator and arranged for operation on a plurality of pole numbers, and means for interconnecting said motors in series with each other to the terminals of said generator.

2. A system of ship propulsion comprisin an alternating current generator, prope er driving means comprising a sin 1e pole number induction motor insulated or the full voltage of said generator and a plural pole number induction motor insulated for less than the full voltage of said generator, and. switchin means for connecting the armature win g of said generator in Y and for connecting said sin le ole number motor in series between sai -connected winding and the high speed terminals of said plural pole number motor.

3. A system of ship propulsion comprismg an alternating current generator, prope er driving means comprisin a sin is pole number induction motor insulated or the full voltage of said generator and a plural pole number induction motor insulated for less than the full voltage of said generator, and switchin means for connecting the armature win in of said generator in Y and said single 0 e number motor in series between said -connected winding and the high speed terminals of. said plural pole number motor, or connect-- 4. A system of ship propulsion comprisin an alternating current generator, prope ler drivin means comprising a sin le pole number mductionmotor insulated or the full voltage of said generator and a plural pole number induction motor insulated for less than the full voltage of said generator, and switchin means connecting the armature win of said generator in Y and said single 0 e number motor in series between said Y-conne'cted for winding andthe high speed terminals of said plural pole number motor, or connectsa1d Y connected winding tothev low speed terminals of said her motor.

5. A system of ship propulsion comprising an alternating current generator, propeller driving means comprising a single pole number induction motor insulated for the full voltage of said generator and a plural pole number induction motor insulated for less than the full voltage of said generator, and switching means for connecting the armature winding of said generator in Y- and said single pole numplural pole number motor in series between said Y-connected winding and the high speed terminals of said plural pole number motor, connecting said Y-connected winding to the low speed terminals of said plural pole number motor, or connecting said generator armature windin in delta to the low speed terminals of said plural pole number motor.

In witness whereof, I have hereunto set my hand this 10th da of May, 1923. CAMPBELL OMILLAN. 

